I think that it has something to do with reducing the corrosion potential in the copper. Without the oxygen it does not corrode in the environment as easily. I used this material before in clean room vacuum pump seals. They had to be oxygen free copper. I am not completely certain, but that is all I remember. The name is kind of a misnomer, it is not that it does not have oxygen, but that it is smelted in a oxygen free evvironment. [sig]<p>Edson Campos<br><a href=mailto:edsoncampos@earthlink.net>edsoncampos@earthlink.net</a><br><a href= > </a><br> [/sig]